Explicitely opens the database connection. This is done to play nice
with DBAL's MasterSlaveConnection. Which, in some cases, connects to a
follower when fetching the executed migrations. If a follower is lagging
significantly behind that means the migrations system may see unexecuted
migrations that were actually executed earlier.

Parameters

Return Value

null|string
resolveVersionAlias(string $alias)

Returns the version number from an alias.

Supported aliases are:
- first: The very first version before any migrations have been run.
- current: The current version.
- prev: The version prior to the current version.
- next: The version following the current version.
- latest: The latest available version.

If an existing version number is specified, it is returned verbatimly.

Parameters

string

$alias

Return Value

null|string

A version number, or null if the specified alias
does not map to an existing version, e.g. if "next"
is passed but the current version is already the
latest.

Parameters

Return Value

protected bool
connect()

Explicitely opens the database connection. This is done to play nice
with DBAL's MasterSlaveConnection. Which, in some cases, connects to a
follower when fetching the executed migrations. If a follower is lagging
significantly behind that means the migrations system may see unexecuted
migrations that were actually executed earlier.